Halogen Activation by Photosensitized Processes in Atmospheric Aerosol Particles

ELEANOR MIKO, Sergey Nizkorodov, University of California, Irvine

     Abstract Number: 204
     Working Group: Aerosol Chemistry

Abstract
Secondary organic aerosols (SOAs) are formed by the photochemical oxidation of primary organic matter and volatile organic compounds (VOCs) in the atmosphere and represent a major fraction of global atmospheric organic aerosols. One particularly uncertain aspect of atmospheric aerosol chemistry is the role of photosensitized processes. In aerosol particles, these processes have been proposed to form halogen atoms and radical ions, which are highly reactive and important oxidizers of both organic and inorganic tropospheric compounds. These products may additionally lead to the formation of halogenated compounds with further implications for tropospheric and stratospheric chemistry. While it is known that some SOA compounds act as photosensitizers, their efficiency in photooxidation of halogen ions has not been investigated, and further research is necessary to develop a more detailed understanding of the mechanisms for photosensitized production of halogen atoms, radical ions, and other halogenated products. For this work, photosensitization by SOA produced from the photochemical oxidation of distinct types of VOCs will be compared: (1) SOA produced by ozonolysis of terpenes, such as ????-pinene, representative of forest environments; (2) SOA from ????-pinene oxidized by OH in the presence of nitrogen oxides, representative of forest air affected by air pollution; (3) SOA from naphthalene, representative of heavily polluted urban air. In addition to these SOA, we will also examine particles produced by burning biomass, representative of air affected by wildfires. Analysis will involve methods such as Ultra-High Performance Liquid Chromatography High-Resolution Mass Spectrometry (UHPLC-HRMS) and Ultraviolet-Visible (UV-Vis) spectroscopy. These experiments are ongoing, and initial results are expected by the time of the AAAR meeting.